Health officials think worst of West Nile has passed

Updated 10:37 pm, Wednesday, September 12, 2012

Although this year's West Nile outbreak is on track to be the deadliest on record, federal health officials said Wednesday they are hopeful the worst is over.

As Bexar County recorded its 16th and 17th cases Wednesday — a 27-year-old woman with the milder West Nile fever and a 68-year-old man with the more serious type — officials said the numbers of reported cases and deaths would continue to rise sharply for a while, even though the actual risk to people was likely falling.

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“One good piece of news is that based on historical data, we've turned the corner on the epidemic,” Petersen said in a conference call with reporters. “Experience is showing us that West Nile virus outbreaks in the United States tend to peak in mid- to late-August.”

While cooler temperatures are a factor in reducing that risk, so are the shorter days of late summer and fall. The mosquitoes that transmit West Nile virus “go into sort of a hibernation phase and stop biting people” when it gets dark earlier, Petersen said.

“People should continue to take preventive measures,” he said. “But we're hopeful that the worst of the outbreak is behind us.”

Those measures include getting rid of standing water that can serve as mosquito breeding grounds, using insect repellant and wearing long pants and long sleeves when outside at dusk and dawn, when mosquitoes feed.

Nationwide, 2,636 cases had been reported to the CDC as of Wednesday — a 35 percent increase from the previous week. Of those, 118 have died. Texans have made up 40 percent of all U.S. cases.

Of more importance to experts is the number of West Nile neuroinvasive cases, which cause encephalitis or meningitis and are most likely to be deadly.

Just over half the U.S. cases are classified as neuroinvasive disease, and those numbers are likely to equal or surpass those of previous years, Petersen said.

“If this year turns out that we'll have the most neuroinvasive disease cases of any year — which is what we're on track for — we would expect that this year would have the largest number of deaths as any year,” he said.